X-ray tube



Sept. 27, 1927. 1,643,453

G. HOLST X-RAY TUBE Filed Auil. 25. 1925 @226 W 4 y iv 7 iflw$ W 74 Inventor,

GILLES HOLST,

PATENT OFFICE.

] EINDEOVEN, NETHERLANDS, ASSIGNOB TO N. V. PHILIlPS GLOEI- LAMPENFABRIEKEN, OE EINDHOVEN, NETHERLANDS. Y

x-nar TUBE.

i Application filed August 25, 1925, Serial No. 52,898, and in the Netherlands November 20, 1924.

This invention relates to an improvement in or modification of that described in specification No. 1,626,465 issued April'26, 1927, and is concerned with incandescent cathode X-ray tubes, more particularly with such as described in the above-mentioned United States Letters Patent.

In X-ray tubes according to the prior specification the incandescent cathode is arranged within a metal vessel the wall of which forms wholly or partly part of the outer wall of the tube and from which the anticathode is separated by an insulation capable of resisting the operating voltage 1 to be supplied between the incandescent cathode and the anticathode, the metal vessel and the anticathode being so shaped and so arranged relatively to each other that the cathode rays can strike the anticathode 2 only on a limited surface.

According to the prior specification, in" )rder to realize the latter object the metal vessel may be narrowed on the side of the anticathode to an aperture for the passage of the cathode rays, that part of the surface of the anticathode which is struck by the cathode rays, being located in or near said aperture.

According to the present invention, the

a erture of the metal vessel is made regulab e. By changing the size of the aperture, the size of the focus, that is to say the'size of that part of the surface of the anticathode which is struck by the cathode rays, is also modified.

X-ray tubes according to this invention offer therefore the advantage that they can be used for diflt'erent purposes. tube can be used, for example, for taking radio'raphs (small focus) and for irr'idiation large focus).

For making the aperture of the metal vessel for the passage of the cathode rays regulable, many different constructions may be used. According to this invention a rotary member provided with means for regulating the aperture, ma be arranged against the wall of the meta vessel on the side of the incandescent cathode. For moving the said rotary member, a movable member may be rovided which can be moved by magnetic influence from outside the tube.

The accompanying drawing illustrates, by way of example, a construction of an K-ray The same tube according to the present invention, in which drawing Figure 1 is a section through the axis of the tube and Figure 2 represents on an enlarged scale part of the device for regulating the aperture in the metal vessel.

The X-ray tube illustrated consists of a double-walled glass tube' 1 to the ends of which an anticathode 2-and a metal vessel 4 are hermetically sealed. The anticathode 2 is provided with a metal tube'3 which serves to supply a cooling liquid. The metal vessel 4 carries a cylindrical wall 5 which protects the seal between the glass vessel 1 and the metal vessel 4.

To the other end of the metal vessel 4 is sealed a glass closing piece 6, an incandescent cathode 7 being mounted Withinthe metal vessel 4 on pole wires 8 and 10 which rest on a metal table 9. The pole Wire 8 is electrically connected to the metaltable whereas the pole Wire 10 is insulated therefrom by a bead 11 of quartz or similar insulating material. Terminals 12 and 13 serve to supply current to the incandescent cathode. To the metal vessel 4 is further connected a metal disc 14 which has an aperture 15 and is so arranged that the mirror of the anticathode 2 is located near the said aperture. For regulating the size of the aperture 15 an iris diaphragm has been provided.

Againstthe bottom surface of the metal disc 14 is provided-a metal ring 18 held by screws 21 and 22 (see Figure "2) which are secured in the disc 14. The ring 18 to which lamellae 24 are secured by means of pins 26 can be turned backwards and' forwards through a certain distance and is provided for this purpose with circular slots 19 and 20 through which pass the screws 21 and 22.

The ring 18 is provided with a gear 17 with which meshes a gear wheel 23, mounted on one end of a spindle 30 which can turn in' bearings 31 and 32 and in the metal table 9. At its other end the said spindle is provided with a conical gear wheel 33 which meshes with a conical gear wheel 34, mounted on a spindle 36 which can turn in a glass tube 35. The spindle 36 has an iron projecting part 37 sothat from the exterior by magnetic influence the spindle can be turned backwards and forwards. The rotation of the spindle 36 causes the'metal ring 18 to rotate owing to which the size of the aperture 15 increases or decreases. The metal disc 14 is provided for this purpose with metal pins on which can pivot semicircular lamellae 24. At the other end these lamel'he are provided with small pins 26 which can turn and can slide to and fro in grooves 27 provided in the ring 18. \Vhen the ring 18 turns, the lamcllae 24 are conse quently carried along, owing to which the size of the aperture 15 either increases or decreases.

An X-ray tube according to the present invention maybe highly evacuated in any known manner or may have a gaseous filling consisting 0t hydrogen or helium at such a pressure that any detrimental ionization does not occur. In the caseofhydrogen this pressure maybe, for example,-0,01' mm. of mercury. I v

When operating an X -ray tuheflas'illustrated a high itQl'lSlOnlS: sup "lied between the metal vessel 4 andvthei-anticathode 2. The

electrons emanating from the incandescent a cathode, are drawn by theelectric field towards the anticathode; Thev shape of the vessel 4 with the disc l4qand the aperture 15, and the arrangementof the anticathode mirror near said aperture cause'the cathode rays to strike only a limitedv surface of the anticathode. The size offthissu rface is regu lated by modifying the "size of the aperture 15. The X-rays generated, pass through the aperture 15, through the aperture in the table 9 and leave'the'- tube through the glass closin iece 6. Undesired X-rays are ab sorbed l iy the wall or the metal vessel 4 which, preferably, consists of chrome-iron.

What I claim is 1. An incandescent cathode X-ray tube in which the incandescent cathode is arranged within a metal vessel the wall of which wholly or partly forms the outer wall of the tube and from which the anticathode is separated by an insulation capable of resisting the operating voltage to be su plied between the incandescent cathode and t to anticathode and in which the metal vessel adjacent the anticathode is narrowed to an a rture for the passage of the cathode rays, t at part of the surface of the anticathode which is struck by the cathode rays being located in or near the said aperture characterized in that the aperture in the metal vessel for the passage of the cathode rays is regulable.

2. Au X-ray tube according to claim 1,.

characterized by a rotary member arranged against the wall of the metal vessel adjacent the incandescent cathode and provided with means for regulating the size of the aperture for the passage of the cathode rays.

3. An X-ray tube according to claim 1 characterized by a rotary member arranged against the wall of the metal vessel adjacent the incandescent cathode and provided with means for regulating the size of the aperture for the passage of the cathode rays, said rotary member being moved by a member which in its turn can be moved by magnetic influence from outside the tube.

In testimony whereof I atfix my signature at the city of Eindhoven, this 10th day of August, 1925.

GILLES HOLST. 

